Invalids, particularly those persons who are completely or almost completely paralyzed, have many important medical problems. These include the development of bed sores which are caused by long continued pressure caused by the weight of the body on areas of the skin in contact with the mattress or sheet. Bed sores, when they occur are dangerous to the health of the invalid. In addition they are difficult to cure and expensive to treat because the fragile condition of the patient requires extra care to move the patient without causing pain or increasing injury.
Heretofore, much thought has been given to the solution of these problems. A basic approach has been to change the distribution of the weight of the body on the bed. Some approaches are illustrated by the United States patents to Munch U.S. Pat. No. 3,742,528, Skeffington U.S. Pat. No. 1,040,795, Lamont U.S. Pat. No. 1,295,770, Rand U.S. Pat. No. 595,734, Groff U.S. Pat. No. 218,016, Italian #471002, and Keathley Sr. U.S. Pat. No. 2,932,831.